Oscillator led indicator

[rhdwave]

Should an led turn on and off when hooked up to an oscillator? What i mean is, you shouldn't need any other input like a guitar signal correct? And the led should be hooked up to where the output for the various waves are (i.e. square, triangle etc...).   Is this correct?
Much thanks!!!

[nooneknows]

if the signal is quite wide and the current is enough, well, yes, it lights up. Keep an eye open over the current you give to the led, add a resistor in series eventually, otherwise you could burn it

[rhdwave]

Yes, well the led lights up, with a resistor in series to protect it, but it doesn't turn on and off as i thought it should with the oscillations...i tried using a pot to vary the resistance with the capacitor so i figured i should have hit a range where the period was long enough to show up on an led with the naked eye...but it just stays on, like it's nothing more than a power indicator.

[nooneknows]

Just one question: are you sure to apply a reverse voltage across the diode during the led-would-be-off time?

[rhdwave]

I did not do that.  How would i accomplish that, just by placing a diode next to the led? in which direction?

thanks again!

[nooneknows]

do you have schematics of the circuit?

[SISKO]

You may have to decuople the led signal with a capacitor (say 1uF) because probably you have  dc and ac both at the same time in the same path.

[rhdwave]

Okay i figured it out...i had the grounds all hooked up to the vref instead of the real ground.  It was kind of confusing for me, as i know with a single battery supply you're supposed to create a virtual ground, but i guess it's really just that...virtual and only for the sake of the positive and negative battery inputs on the opamp, and the virtual ground i have going into the non-inverting input of theopamp.  So, it's cool, it oscillates and the led shows it all now.  I'm just learning about oscillating circuits, so i wanted to something real simple to work on and experiment with...so this is the circuit:  just a simple square wave oscillator



Now if i wanted to make a triangle wave, could i just take the output from another spot, or do i need to hook this up to another opamp and if so, anyone know how? Also, if i hook the output of this up to an oscilloscope will i see the square wave, or do i need to add some kind of audio signal to do that? 

Any responses are greatly appreciated...Much thanks!!!

[SISKO]

About the triangle wave, i dont know i think taht this is posible only with integrators, but i dont have any expierence with that circuit.

As far for the oscilloscope, yes you should see the squeare wave at the the ouput and maybe youll find some path with the triangle (or something similar) that youre saying.
Oh!, and theres no need for an audioprobe

[slacker]

If you take the signal from the top of the capacitor you get a triangle wave. You need to buffer it though if you want to drive an LED.

[rhdwave]

Thanks Slacker! I'll check that out...i just got the software oscilloscope and i'm going to hook everything up to see how things look...